Organic light emitters based on multiresonance-induced thermally activated delayed fluorescent materials have great potential for realizing efficient, narrowband organic light-emitting diodes (OLEDs). However, at high brightness operation, efficiency roll-off attributed to the slow reverse intersystem crossing (RISC) process hinders the use of multiresonance-induced thermally activated delayed fluorescent materials in practical applications. Here we report a heavy-atom incorporating emitter, BNSeSe, which is based on a selenium-integrated boron–nitrogen skeleton and exhibits 100% photoluminescence quantum yield and a high RISC rate (k_RISC) of 2.0 × 10⁶ s⁻¹. The corresponding green OLEDs exhibit excellent external quantum efficiencies of up to 36.8% and ultra-low roll-off character at high brightnesses (with very small roll-off values of 2.8% and 14.9% at 1,000 cd m⁻² and 10,000 cd m⁻², respectively). Furthermore, the outstanding capability to harvest triplet excitons also enables BNSeSe to be a superior sensitizer for a hyperfluorescence OLED, which shows state-of-the-art performance with a high excellent external quantum efficiency of 40.5%, power efficiency beyond 200 lm W⁻¹, and luminance close to 20,0000 cd m⁻².

基于多共振诱导的热激活延迟荧光材料的有机发光体在实现高效、窄带有机发光二极管 (OLED) 方面具有巨大潜力。然而，在高亮度工作时，由于缓慢的反向系统间穿越（RISC）过程导致的效率下降阻碍了多共振诱导的热激活延迟荧光材料在实际应用中的使用。在这里，我们报告了一种重原子结合的发射体BNSeSe，它基于硒整合的硼-氮骨架，具有100% 的光致发光量子产率和2.0 × 10 ⁶  s ^{-1的高RISC 率（} k _{RISC ）。}. 相应的绿色 OLED 在高亮度下表现出高达 36.8% 的出色外量子效率和超低滚降特性（在 1,000 cd m ^-2和 10,000 cd m ^{-下滚降值非常小，分别为 2.8% 和 14.9%） 2}，分别）。此外，捕获三重态激子的出色能力还使 BNSeSe 成为超荧光 OLED 的卓越敏化剂，它显示出最先进的性能，具有 40.5% 的出色外部量子效率，功率效率超过 200 lm W ^{- 1}，亮度接近20,0000 cd m ^-2。